John Swift, who moved to the Hawthorns after his Reading contract expired, was in the perfect place to turn in his first goal for the Baggies five minutes after half-time.
That goal, laid on by another summer recruit, former Millwall man Jed Wallace, canceled out Middlesbrough’s 10th-minute opener from Isaiah Jones.
It was a much better second half display from West Brom after manager Steve Bruce had watched Boro control most of the first half.
The hosts named striker Marcus Forss on the bench following his move from Brentford on Thursday. Zack Steffen, Darragh Lenihan and Ryan Giles all started for the first time since moving to the Teesside club.
Steffen was involved plenty too. The goalkeeper, on loan from Manchester City, was alert to make amends for straying from his line by brilliantly turning Wallace’s excellent effort from the touchline onto the bar.
Boro led soon after. When West Brom’s attempts to move forward broke down, the hosts attacked through Giles. The Wolves loanee’s pass into the penalty area was turned across the face of goal by striker Chuba Akpom for Jones to finish from six yards.
After that the home side controlled much of the play and looked more dangerous but wasted numerous good positions so West Brom remained in the game.
The best of those openings arrived nine minutes before the break when Giles was again involved. After Matt Crooks had picked the wing-back out on the left, his low delivery into the six-yard box seemed perfect but Duncan Watmore did not connect properly and the ball went wide.
There was still time for Marc Bola to sting the palms of David Button from distance, but the onus was on West Brom to improve after the restart to avoid an opening day defeat.
The visitors were a different proposition after the restart and equalized early on.
Jayson Molumby fed Wallace down the right and his lovely run and cutback into the area was perfect for Swift to side-foot beyond Steffen from 12 yards.
Swift was then denied a second within a couple of minutes when his trickery in the box created an opening and Steffen was alert to stop at his near post.
Despite West Brom’s improvements, Bruce was cautioned and Middlesbrough grew stronger again after that.
Forss, introduced from the bench for his debut, fired an effort wide, while Jonny Howson had an effort deflected just wide when Button was wrong-footed.
However, by the full-time whistle West Brom had gone close a couple more times and Boro should be just as happy with a point as the visitors.